Z94.2 - Anthropometry & Biomechanics: Biomechanics Section

CAPITULUM OF HUMERUS. A smooth hemispherical protuberance at the distal end of the humerus (q.v.) articulating with the head of the radius. Irritation caused by pressure between the capitulum and head of the radius is called tennis elbow. (See RADIOHUMERAL JOINT.)

CARBON DIOXIDE. The gaseous product of oxidation or aerobic metabolism (q.v) CO2 (chemical symbol) is transported in the plasma of venous blood to the lungs for discharge. Its partial pressure, p CO2, controls many body functions including respiratory rate and cardiac rate.

CARDIAC RATE. Heart beats per minute (BPM). The heart can change its output by increasing its stroke volume or its cardiac rate, where the latter is the most effective and most efficient method. Heart rate varies widely with age, sex, environmental stress, state of health, etc. Therefore, the term "normal" heart rate is meaningless. However, ratio of working cardiac rate over resting cardiac rate is one of the measures of work tolerance and work stress.

CARPAL TUNNEL. A passage in the wrist through which important blood vessels and nerves pass to the hand from the forearm. The carpal tunnel is comprised of the concave surfaces of the palmar carpal bones covered by the transverse carpal ligament. The carpal tunnel acts as the conduit for the flexor tendons, the median nerve, and the median artery. Ulnar or radial deviation cause misalignment of the carpal tunnel and irritation of structures passing through it. (See CARPAL TUNNEL SYNDROME.)

CARPAL TUNNEL SYNDROME (CTS). A common affliction of assembly workers caused by compression of the median nerve in the carpal tunnel. The symptoms of carpal tunnel syndrome are burning, numbness, tingling, and pain in the thumb, index and long fingers and in the lateral half of the palm. The thenar eminence may be emaciated. Symptoms are generally felt at night, and may wake the individual from sleep. The pain may radiate to the arm and up into the shoulder following the median nerve path. These symptoms are produced by an entrapment of the median nerve in the carpal tunnel. CTS results from disease either from small or restricted carpal tunnel which compromises the contents, or an enlargement of one of the structures in the canal. CTS is correlated with vibratory hand tool usage, jobs requiring considerable use of the hands, such as assembly work. Results in reduced manipulative skills, particularly if thumb is involved and often reduces work output. Marie and Foix in 1913 first recognized the surgical methods of decompression of the medial nerve to prevent paralysis of the thenar muscles. Medical awareness began in the 1930's, when surgical techniques were first refined. In the 40's and 50's, general recognition surfaced.

CARTILAGINOUS PLATES. Flattened masses of cartilage which act as supporting structures. Intervertebral discs (q.v.) are separated from the vertebrae by cartilaginous plates.

CENTER OF GRAVITY. Equilibrium point of a supported body where all its weight is concentrated (See CENTER OF MASS).

CENTER OF MASS. That point at the exact center of an object's mass; often called the center of gravity (See CENTER OF GRAVITY).

CENTER OF ROTATION. A point around which circular motion is described.

CEREBELLUM. The "small brain" located below the cerebral hemispheres. It exerts a regulatory influence of muscular activity and is concerned with balance, posture, and muscular coordination. It is a subdivision of the mentencephalen, which grows upward and outward from the axis of the brain stem to hide the more inferior portions not covered by the cerebral hemispheres.

CEREBRUM. The anterior-superior part of the brain which governs voluntarily coordinated activities of the body, e.g., sensory-motor functions and associative activities. It is the main portion of the brain, occupying the upper part of the cranial cavity. Its two hemispheres, united by the corpus callosum (also known as commissura magna cerebri), form the largest part of the human nervous system.

CHEMOTAXIS. Relating to contact with a chemical environment. A primary consideration of environmental health, e.g., air pollution. One of the ecological stress vectors.

CHRONOCYCLEGRAM. The photographic record made by a chronocyclegraph, (q.v.).

CHRONOCYCLEGRAPH. An instrument for measuring the pathway taken by a body reference point or an object during the performance of a task as part of the work cycle. It consists of a flickering light attached to an anatomical reference point (q.v.) and photographic recording of the moving light. The chronocyclegraph enables an investigator to determine exact speed, relative speeds and directions as well as changes in motion such as may be caused by fatigue.

CLAVICLE. The collarbone. The sole bony connection between the arm and the trunk. It is easily fractured in falls broken by an extended arm.

CONDITIONED REFLEX. Patterned reflex response to an external stimulus developed as a result of either habituation or training. Easier to learn than to unlearn, e.g., stop on red, go on green. (See SIMPLE REFLEX.)

CONDUCTIVE DEAFNESS. Impaired hearing resulting from interference with, or injury to, the mechanisms for the conduction of sound waves into the inner ear. This transmission takes place either through the external auditory canal and the structures of the middle ear (air conduction) or through vibrations applied to the bones of the skull (bone conduction). This type of hearing loss can be contrasted with Boilermaker's Deafness which is due to perceptive deafness (q.v.).

CONTRACTILE TISSUE. Tissue which is capable of shortening in response to physiological or environmental stimuli, E.g., muscle.

CONTACT GRASP. Action of the hand when pushing, e.g., a coin over a flat surface. One of the five basic grasps of the hand. Not a grasp in the literal sense. The index finger is generally used. Overuse may contribute to high stress concentration on base of distal phalanx and physical damage.

CORONAL PLANE. Any plane which divides the body into anterior and posterior portions. It is perpendicular to the sagittal and transverse planes (q.v.) and is also known as the frontal plane.

CORONOID FOSSA. A depression in the lower end of the front of the humerus in which the coronoid process of the ulna lies when the arm is bent.

COVERT LIFTING TASK. An operation which may not involve the handling of a load but which exhibits all of the biomechanical characteristics ascribed to an overt lifting task (q.v.). Its principal characteristic resides in the existence of a bending moment acting on the vertebral column for reasons other than load lifting, e.g., excessive heel height may cause postural changes which impose bending moments on the lumbar spine. Side-stepping may impose a lateral bending moment. Reaching forward constitutes covert lifting task because torque of the arm at the shoulder joint is transferred to the vertebral column. (See LIFTING TASK).

CUMULATIVE TRAUMA. The development of trauma or work strain from repeated or continuous application of work stress which for short periods of time or single applications would not be harmful. An important factor to consider in workplace and tool design. This does not include delayed onset muscle soreness.